Question

What convinced Inca armies to retreat in their war against the Spanish in 1533

Answer 1

Horses, iron swords and guns, which had not been known in Americas when the Spanish arrived

Answer 2

Another thing was the spanish sheer manpower as they had more than the incas. They also were better prepared since they had big ships. Another thing they had was disease as they landed in the americas incans caught disease. Also their leader was captured and thrown in prison. He died shortly weaking the unity of the empire. Within a year they fell.